Control apparatus for application of automatic air brake systems

ABSTRACT

A system for remotely controlling in discrete increments the application of pneumatic braking force in an automatic air brake system of a train, to precisely control the amount of braking force applied for a given train length. A plurality of vessels with associated electrically controlled valves is provided to progressively reduce the pressure in a pilot reservoir by expanding the volume of a communicating network, the degree of expansion in volume being determined by the combination of vessels sequentially added in parallel to the reservoir by control of the associated electrically controlled valves. Brakes are applied by removing electrical energy, whereby loss of power or failure of a circuit will automatically increase braking to an emergency level.

Sept. 4, 1973 CONTROL APPARATUS FOR APPLICATION OF AUTOMATIC AIR BRAKESYSTEMS Primary Examiner-Duane A. Reger Attorney-Walter C. Bernkopf [57]ABSTRACT A system for remotely controlling in discrete increments theapplication of pneumatic braking force in an automatic air brake systemof a train, to precisely control the amount of braking force applied fora given train length. A plurality of vessels with associatedelectrically controlled valves is provided to progressively reduce thepressure in a pilot reservoir by expanding the volume of a communicatingnetwork, the degree of expansion in volume being determined by thecombination of vessels sequentially added in parallel to the reservoirby control of the associated electrically controlled valves, Brakes areapplied by removing electrical energy, whereby loss of power or failureof a circuit will automatically increase braking to an emergency level.

11 Claims, 5 Drawing Figures smnur'a mm WN PATENIEDSE? 41915 3756365.

SHEEI 2 (IF 3 gig PATENTEB REF 4 I975 sum 3 or 3 MALAY S E W%AAYYA w T 4W 'AA" A M 7 A'Y'A ED D E M RFENI23A GO E EPPP DRLEEEL E TTE SSRENERGIZED; DE-ENERGIZED) CONTROL APPARATUS FOR APPLICATION OF AUTOMATICAIR BRAKE SYSTEMS BACKGROUND OF THE INVENTION This invention relatesgenerally to pneumatic brake systems and more particularly to automatic,air brake systems for remote controlled railroad trains.

A commonly known scheme in air brake systems provides for automaticapplication of brakes upon the reduction of pressure in a charged brakepipe extending the length of the train. The advantages of such a system,wherein the braking force is inversely proportional to the brake pipepressure, is that a fault in the system as for example, a burst airhose, will automatically cause the brakes to be applied, thus alwaysensuring a safe condition of operation with regard to the integrity ofthe overall brakeage system. This is accomplished by providing at eachcar an auxiliary reservoir selectively communicating through a valvewith the brake pipe or the brake cylinders on the car. The reservoir ischarged to a constant pressure when communicating with the brake pipeunder released brake conditions, and is discharged to activate thebrakes by communication with a release of pressure to the brakecylinders.

Reduction of brake pipe pressure with consequent application of thetrain brakes is occasioned by the engineers opening of a brake valve toexhaust air from the brake pipe to the atmosphere. In order to eliminatethe need for the engineer to leave the valve open for a long period oftime, the time being dependent on the train length, an equalizingreservoir and associated discharge valve are provided. The dischargevalve maintains the air pressure in the brake pipe at a levelcorresponding to that of the equalizing reservoir. The desired level ofbrakeage can then be applied by selective control of the brake valve todirectly regulate the pressure in the equalizing reservoir, irrespectiveof the train length. When the brake valve is set so that the brakes arereleased the equalizing reservoiris fully charged from the compressor toa pressure corresponding to that in the brake pipe and auxiliaryreservoir, whereas, when it is set to effect maximum braking, theequalizing reservoir is caused to exhaust completely to atmosphericpressure the time of exhaustion being always the same and not dependenton train length. Any intermediate brakeage levels desired are set byproper regulation of the time duration in which the brake valve is leftopen.

Various schemes have been used to control braking in this manner. Inautomated systems the brakes are commonly set by means of controlsignals which are time modulated, thus again requiring the operator toconsciously, or at least instinctively, apply the signals for a specificperiod of time to obtain a given braking effort. The greatestdisadvantage of such an arrangement is the attention that must be givenby the operator. Even if he is skilled with respect to brakeage levelsand corresponding required time periods of application, he must stillremain attentive during the period between the application and releaseor lapping (wherein the equalizing reservoir is neither discharged norcharged) of the controls.

As for completely automated systems, wherein a train automaticallyreceives signals to bring about propulsion or braking as a function ofconditions, such as train length, load, and grade, it is desirable toprovide for a plurality of sequential steps in the level of brakingeffort. The use of a plurality of pressure switches, selectiveactivation of which would allow specific levels of pressure and brakeageto be applied, is a possible means. These pressure switches arepotentially troublesome with respect to operation and maintenance and'are considered less desirable for use in such a system wherein safetyis considered to be of prime importance.

The use of electrical or pneumatic devices to control brakeage, carrieswith it the possibility of a malfunction in the system. If that shouldoccur, it is desirable to bring about a corresponding application ofbrakes, rather than a loss of all braking capability. Various switchingarrangements now in use do not provide for this important feature.

It is therefore an object of this invention to provide an automatic airbrake system which requires a minimum of attention from the operator.

Another object of this invention is the provision in an automatic airbrake system for a plurality of levels of brakeage to be available forapplication.

Yet another object of this invention is the provision therein forrapidly applying a desired brakeage level without need for timemodulation of control equipment. I

Still another object of this invention is the provision foran automaticbrake system which permits discrete stepped reduction of air pressure bymeans of signal pulses whose time duration does not have to bemodulated.

A further object of this invention is the provision for an automatic airbrake system which automatically applies an appropriate degree ofbrakeage when 21 malfunction occurs in the system.

Yet another object of this invention is the provision in an automaticair brake system for control apparatus which is economical to construct,simple in operation and reliable in use.

These objects and other features and advantages become more readilyapparent upon reference to the following description wherein taken inconjunction with the appended drawings.

SUMMARY OF THE INVENTION The subject invention provides for a systematicreduction of pressure in discrete increments, to precisely control theamount of braking force that is applied throughout the train. Aplurality of vessels of predetermined volume are adapted to be connectedin parallel and communicate with the pilot reservoir (equalizingreservoir), by actuation of associated valves. Access of the pilotreservoir to each of the vessels is controlled by a magnet valve, withthe valves being independently activated in a predetermined sequence toexpand the volume, decrease the pressure in the brake pipe, and actuatethe brakes to the degree desired. Such a system In the drawings ashereinafter described a preferred embodiment is depicted; however,various other modifications alternate constructions can be made theretowithout departing from the true spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagramatical illustrationof a pneumatic brake system in accordance with the preferred embodimentof this invention.

FIG. 2 is a diagram of the brake valve portion thereof when in thereleased brake condition.

FIG. 3 is a diagram thereof when in the applied brake condition.

FIG. 4 is a schematic illustration of the controlled expansion portionof the invention.

FIG. 5 is a tabular representation of magnet valve actuation conditionwith respect to brakeage level condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now made to FIG. 1wherein an automatic air brake system, of the type commonly used onrailway trains, is shown as modified by the preferred embodiment of thisinvention.

Briefly, the invention portion comprises a part of the apparatus 11which is located aboard the locomotive (not shown) and is used tocontrol the application of brakes to each of a plurality of railway carshaving individual car brake assemblies 12.

An air compressor 13 driven by a prime mover such as an electric motor(not shown) supplies air to a main reservoir 14 and maintains asubstantially constant pressure therein by way of a compressor governor16. The governor is commonly an air-pressure controlled switch whichcloses at a cut-in pressure and opens at a cut-out pressure. Typically,a pressure of 85-100 psi is maintained in the main reservoir, andapressure reducing valve 17 is inserted between the reservoir and thebrake valve 18 to provide a lower constant pressure to the brake valve18.

Independently communicating with the brake valve 18 is a brake pipe 19and an equalizing reservoir 21. The brake valve 18 is a valve whichfunctions to develop or dissipate pressure in the equalizing reservoir21 in proportion to the degree of movement on the handle quadrant of thebrake valve 18. In turn, pressure in the brake pipe is developed andexhausted by a relay valve that is piloted by the equalizing reservoirpressure, maintaining the same pressure condition in the brake pipe 19that exists in the equalizing reservoir 21. A duplex air gauge 22provides an indication of the pressure in both the main reservoir andthe brake pipe.

The brake pipe 19 extends the length of the train, with sections of hose23 interconnecting the individual cars. Cocks 24 are disposed on eachend of the cars to close off the brake pipe when desired.

Individual car brake assemblies 12 communicate with the brake pipethrough a branch pipe 26 and comprise a triple valve 27 operablyconnected to an auxiliary reservoir 28, a brake cylinder 29 and thebranch pipe. Such an assembly is adapted for use in automatic air brakesystems wherein the train brakes are automatically applied when a faultoccurs in the pneumatic circuit, as for example when the hoseconnections between cars are broken. A reduction in brake pipe airpressure causes an application of the brakes, while a charging with airtends to release them. In operation, the brake pipe is charged by asetting of the brake valve 18 on the locomotive. The pressure in thebranch pipe 26 operates the triple valve 27 which connects the brakecylinder 29 to an exhaust port to release the car brake, and theauxiliary reservoir 28 to the brake pipe 19 to be chargecd to a likepressure. Application of the brakes is made when the brake valve 18 ispositioned to exhaust air from the brake pipe (in the service position).Falling pressure causes the triple valve 27 to operate this time todisconnect the auxiliary reservoir 28 from the brake pipe 19, close offthe brake cylinder exhaust port, and connect the auxiliary reservoir 28to the brake cylinder 29. As long as the brake pipe 19 pressure isfalling, the auxiliary reservoir 28 is connected to the brake cylinder29. Its air, typically at an original pressure of at least psi, flowsinto the brake cylinder 29, forces the piston out, and applies thebrake. As the pressure in the brake pipe 19 and auxiliary reservoir 28falls, the brake cylinder pressure rises, eventually to an equal valueif application is continued. Typically, on a system wherein theauxiliary reservoir 28 is charged to 70 psi, to make a full serviceapplication of the automatic brake, it is only necessary to reduce thebrake pipe pressure from 70 psi to 50 psi, thus causing a pressure of 50psi to be applied to the brake cylinders 29.

If the brake pipe pressure reduction is stopped in the range between thefully charged condition and the equalization point where brake pipe,auxiliary reservoir, and brake cylinder pressure are all equal, thetriple valve 27 operates to set-up a lap position wherein the brakecylinder 29 is disconnected from the auxiliary reservoir 28, but is notconnected to exhaust, thus leaving the brakes partly applied in trainsemploying direct release type car brakes. The triple valve 27 will onlylap" on falling brake pipe pressure of an application, not on risingpressure of a release. As a consequence, a partial release cannot bemade. That is, raising the brake pipe pressure will cause a fullrelease. Brakes can be reapplied without recharging, but only to thelevel provided by the remaining air in the car reservoirs. If the carreservoirs are down to 50 psi, the brake pipe must be lowered below 50to reapply brakes. By carrying brake pipe pressure at say psi, severalapplications are possible in quick succession. However, there are otherdisadvantages that result from carrying these higher pressures.

Without the equalizing reservoir 21 it would be necessary when applyingthe brakes, to leave the brake valve 18 in the service position untilthe brake pipe 19 has been exhausted to the desired pressure. In a longtrain the time would be significant, and the engineer would have toclosely watch the brake pipe gauge to know when his reduction was made.Provision was thus made, to use as a pilot, an equalizing reservoir 21',communicating with the brake valve 18 as shown in FIGS. 2 and 3. Tofacilitate the arrangement an equalizing piston 31 (a relay valve) isused to equalize the pressure in the equalizing reservoir 21 with thatin the brake pipe 19. The former is connected to the top side of theppiston and the latter to the underside thereof. The equalizing piston 31is adapted to operably move up or down in response to the pressuredifference between the equalizing reservoir 21 and the brake pipe 19,with its position controlling the exhaust of air from the brake pipe,and consequent decreases in pressure therein.

Referring to FIG; 2, the brake valve 18 is shown in a released position,wherein the brake pipe and equalizing reservoir are being charged to anequal pressure. The equalizing piston 31 then remains in the downposition as shown, and air from the main reservoir flows to the brakepipe and reservoir as indicated by the arrows. Each time that the brakesare applied and then released it is necessary to recharge the system inthis manner. A valve (not shown) provides for periodic rechargingnecessitated by brake line leakage to pressures below the fully chargedcondition.

When the brake valve 18 is placed in the service condition, theequalizing reservoir commences to exhaust through the port 32 of FIG. 3.The resultant reduced pressure at the top of the piston 31 causes it tobe pushed up by the higher brake pipe pressure. This opens a dischargevalve 33 on the lower end of the piston 31, thereby connecting the brakepipe to a separate exhaust port 34 as shown by the arrows in FIG. 3.Brake pipe pressure is thus reduced and the brakes applied to acorresponding extent. If the brake valve is left in the serviceposition, the reservoir pressure will be reduced to a minimum and thebrake will be applied to the fullest extent. In a system without anequalizing reservoir, the time for'which it would be necessary to leavethe valve in the service position would be great, depending on thelength of the train, whereas with an equalizing reservoir, the timerequired to reduce this pilot pressure to a given point is constant. Thetime to exhaust the brake pipe will not be affected, but the equalizingreservoir allows an operator to more quickly arrive at a degree of brakesetting and then take action to limit it to that degree.

Limiting the brakeage level is accomplished by moving the brake valve toa lap position, wherein the equalizing reservoir is neither dischargednor charged and remains at the pressure to which it was reduced. As longas the brake pipe pressure on the underside of the equalizing piston isgreater than the equalizing reservoir pressure, the piston is up and thebrake pipe is connected to exhaust to atmosphere. As soon as thepressures are equalized the piston 31 moves down, closing the dischargevalve 33 and lapping off the brake pipe from the atmosphere. The time ittakesfor the equalizing piston to drop depends on the train length, butthe time that it takes to set the desired degree of braking (i.e., thetime that the brake valve must remain in the service position beforebeing moved to the lap position) is the same for a given degree ofbraking.

As mentioned hereinabove, an inherent characteristic of the directrelease type of car equipment is that once the brakes have been appliedand released they cannot be reapplied until the brake pipe and auxiliaryreservoir have been fully recharged, which may involve a considerabletime period. Consequently, since a release of the brakes can t begraduated, it is imperative that they are not over-applied. If they are,it would be necessary to either leave them at that level, or fullyrelease them, recharge the system and reapply them to a lesser degree.Such a situation may arise if the operator is distracted or forgetsduring the time the valve is in the service" position.

It is therefore advantageous to provide for a plurality of predeterminedand discrete levels of braking to be applied by control of theadditional pneumatic network 10 shown in FIG. 1.

An equalizing reservoir pipe 36 extends between the reservoir 21 and anexhaust valve 37, which selectively establishes communication witheither a charging pipe 38 or an expansion manifold 39. The exhaust valveis preferably of the magnetic type which lends itself to remote controloperation.

Air flows along the charging pipe 38 from the brake valve 18 to theequalizing reservoir during periods when the exhaust valve 37 is in thereleased position, and the system operates as described hereinabove,with the equalizing reservoir pipe 36 leading to the upper side of theequalizing piston. During periods wherein the exhaust valve 37 is in theapplication position, air flow from the charging pipe 38 is shut off andair is exhausted from the reservoir 21 through the pipe 36 to theexpansion manifold 39. Connected in parallel to the expansion manifold39 is a plurality of vessels 41, 42, and 43 of predetermined constantvolumes. Access to the vessels 42, 43, and 44 from the expansionmanifold 39 is controlled by independently operating control valves 44,46 and 47 respectively preferably of the magnetically activated type. Byselective actuation of these valves, the accessible volume, into whichthe equalizing reservoir can be exhausted, is expanded, and hence thepressure therein is reduced to a corresponding degree to causeapplication of the brakes. A choke 40 may be installed in the manifold39 to limit the rate at which air pressure decreases.

Specific design characteristics of the system may be met by properselection of the number and respective sizes of the vessels utilized.For example, in a system having a 220 cu. in. reservoir it may bedesirable to have available discrete braking steps occasioned byprogressive brake pipe pressure reductions of 6, l3, and 20 lbs.Accordingly, the number of constant volume vessels required would bethree, with volumes of .20, 30, and 38 cu. in. adapted to besuccessively utilized in that order. Any number of vessels may beutilized to obtain as many discrete braking steps. One has only to setthe desired brakeag e level by the proper selection of magnet valves tobe activated, and no time modulation is required to arrive atthat'desired level.

The system may be made to operate in a manual mode, wherein the operatorleaves brake valve 18 in the released position and makes the properselection and settings of thevalves 37, 44, 46 and 47. However, thetrend is toward automation, and the subject system lends itself toremote control, since a simple electrical signal may be used to operatethe magnetvalves. FIG. 4 is a schematic illustration of the valveportion of a system which is adapted for use in an automated system. Useif made of magnet valves of the conventional type, wherein a springbiased plunger is moved by the energization of a solenoid. It iscontemplated that such a system would be automatically controlled byelectrical signals generated in response to change in the railwayprofile. Other factors, such as train length, load weights, desiredspeeds, and anticipated stopping points, would of course be relevant toprogramming the brake control functions.

As is schematically shown in FIG. 4, the magnet valves 37, 44, 46, and47 each have an upper and a lower part, a and b respectively, and areoperable to be functional in either of the two positions by verticalmovement thereof. The positions shown are those appropriate for areleased brake condition, with parts 37b, 44a, 46b, and 47b being in thefunctional condition. The master magnet valve 37 is in the actuated po-I sition to direct the air flow from the charging pipe 38,

to the equalizing reservoir pipe 36, for a charging of the reservoir.The remaining magnet valves 44, 46, and 47 are positioned so as toexhaust the vessels 41, 42, and 43, respectively to the atmosphere.

It should be noted that while operating in an automated mode, withmovement of the valves being remotely controlled, the brake valve 18 isset in the released position and left there, since its function is noweffected by the magnet valves. As a safety measure, provision is madefor a bypass pipe 48 having a check valve 49 inserted therein, to bypassthe exhaust valve 37. Without this check valve 49, once the exhaustvalve 37 is de-energized movement of the brake valve 18 would have noeffect. With its installation there is provided a manual override whichmay be used to increase the brakeage by exhausting the equalizingreservoir through the brake valve.

Also of note is the actuation scheme of the magnet valves, whereby thebrakes are applied by opening circuits or removing electrical energy,thus causing increased braking rather than loss thereof in the eventthat a loss of power or brakeage of a wire occurs. Illustrated in FIG.is a table in which is indicated for each degree of brake setting theactuation condition of each of the magnet valves. In the event that anyone of the valves fails to actuate as desired, brakeage will be effectedto a degree equal to or greater than that desired.

When in the brake-released condition as shown in FIG. 4, the magnetvalves 37, 46, and 47 are actuated while magnet valve 44 is not.Malfunction of valves 46 and 47 will not effect the system in thiscondition, but malfunction of valve 37 will cause air to be exhausted tothe atmosphere through port 44a.

A first brakeage step is occasioned by de-energizing exhaust valve 37and energizing valve 44, thus bringing into use the ports 37a and 44b.The exhaust manifold 39, is then charged and vessel 41 receives a givenvolume of air (e.g., 20 cu. in.) to reduce the pressure in thereservoir, and hence in the brake pipe by a given value (e.g., 6 psi.).Again, if magnet valve 44 fails to actuate, air will be exhausted to theatmosphere through port 44a and a greater degree of braking will beinitiated.

if further braking isdesired magnet valve 46 is deenergized and vessel42 is available for expansion of air from the manifold 39 through theport 46a. Air pressure in the reservoir 21 is decreased a correspondingamount and the degree of brakeage is increased accordingly. Similarly,if still further braking is desired magnet valve 47 is de-energized anda third degree of brakeage is effected. It is important to note that thelast two steps are initiated by de-energization of the magnet valvesrather than the energization thereof. Power losses will then causeover-reaction of the system rather than the opposite. Release of thebrakes is then accomplished by returning the valves to the initialposition with valves 37, 46, and 47 in an actuated condition and valve44 is a de-actuated condition.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An improved pneumatic brake system of the type having a source ofcompressed air, means for charging to predetermined pressures from thesource, both an equalizing reservoir and a brake pipe, equalizing valvemeans sensitive to the pressure difference between the brake pipe andthe equalizing reservoir to exhaust the former to pressure equal to thatin the latter, exhaust valve means for selectively exhausting thereservoir to predetermined pressures, and a plurality of brake cylindersoperably communicating with the brake pipe to apply brakes in responseto pressure reduction therein, wherein the improvement comprises:

a. an exhaust manifold selectively communicating with the equalizingreservoir through the exhaust valve;

b. a plurality of constant volume vessels adapted to be connected inparallel to said exhaust manifold;

c. control valve means for discretely connecting said vessels to saidexhaust manifold in various selected combinations so as to decrease thepressure therein by an amount related to the combined vessel volume,thereby providing a plurality of selected degrees of braking effort tobe applied in the system.

2. A pneumatic brake system as set forth in claim 1 and including vesselexhaust valve means for selectively exhausting each of said plurality ofconstant volume vessels to the atmosphere.

3. A pneumatic brake system as set forth in claim 2 wherein said vesselexhaust valve means is integral with said control valve means andcomprises a plurality of independently activated duplex valves operablein one position to exhaust their associated vessel, and in the otherposition to establish communication between said vessel and said exhaustmanifold.

4. A pneumatic brake system as set forth in claim 3 wherein each of saidplurality of duplex valves is electrically energized, and furtherwherein, in its energized condition, it terminates communication fromthe exhaust manifold to its associated vessel and said vessel isexhausted to the atmosphere, whereas in its deenergized condition itestablishes communication between its associated vessel and said exhaustmanifold.

5. A pneumatic brake system as set forth in claim 1 and including atleast one constant volume vessel connected directly to said exhaustmanifold so as to communicate directly therewith.

6. A pneumatic brake system as set forth in claim 5 and including aduplex valve connected to said exhaust manifold in parallel with said atleast one constant volume vessel, said duplex valve being operable inone position to exhaust said exhaust manifold to the atmosphere, and inthe other position to close-ofi' such exhaust.

7. A pneumatic brake system as set forth in claim 6 wherein said duplexvalve is electrically energized and further wherein, in its de-energizedcondition it exhausts said exhaust manifold, whereas in its energizedcondition it closes off such exhaust.

8. A pneumatic brake system as set forth in claim 1 wherein said exhaustvalve means is integral with said equalizing reservoir charging means.

9. A pneumatic brake system as set forth in claim 8 wherein said exhaustvalve means comprises a duplex valve operable in one position to connectthe source of compressed air to the equalizing reservoirfor the chargingthereof, and in the other position to disconneet the source ofcompressed air and connect the exhaust manifold to the equalizingreservoir for the exhaustion thereof.

and including a bypass in parallel with the exhaust valve said bypasshaving a check valve therein and providing fluid communication from theequalizing reservoir to the source of compressed air, thereby providinga means of exhausting the equalizing reservoir by proper manipulation ofthe charging means.

1. An improved pneumatic brake system of the type having a source of compressed air, means for charging to predetermined pressures from the source, both an equalizing reservoir and a brake pipe, equalizing valve means sensitive to the pressure difference between the brake pipe and the equalizing reservoir to exhaust the former to pressure equal to that in the latter, exhaust valve means for selectively exhausting the reservoir to predetermined pressures, and a plurality of brake cylinders operably communicating with the brake pipe to apply brakes in response to pressure reduction therein, wherein the improvement comprises: a. an exhaust manifold selectively communicating with the equalizing reservoir through the exhaust valve; b. a plurality of constant volume vessels adapted to be connected in parallel to said exhaust manifold; c. control valve means for discretely connecting said vessels to said exhaust manifold in various selected combinations so as to decrease the pressure therein by an amount related to the combined vessel volume, thereby providing a plurality of selected degrees of braking effort to be applied in the system.
 2. A pneumatic brake system as set forth in claim 1 and including vessel exhaust valve means for selectively exhausting each of said plurality of constant volume vessels to the atmosphere.
 3. A pneumatic brake system as set forth in claim 2 wherein said vessel exhaust valve means is integral with said control valve means and comprises a plurality of independently activated duplex valves operable in one position to exhaust their associated vessel, and in the other position to establish communication between said vessel and said exhaust manifold.
 4. A pneumatic brake system as set forth in claim 3 wherein each of said plurality of duplex valves is electrically energized, and further wherein, in its energized condition, it terminates communication from the exhaust manifold to its associated vessel and said vessel is exhausted to the atmosphere, whereas in its de-energized condition it establishes communication between its associated vessel and said exhaust manifold.
 5. A pneumatic brake system as set forth in claim 1 and including at least one constant volume vessel connected directly to said exhaust manifold so as to communicate directly therewith.
 6. A pneumatic brake system as set forth in claim 5 and including a duplex valve connected to said exhaust manifold in parallel with said at least one constant volume vessel, said duplex valve being operable in one position to exhaust said exhaust manifold to the atmosphere, and in the other position to close-off such exhaust.
 7. A pneumatic brake system as set forth in claim 6 wherein said duplex valve is electrically energized and further wherein, in its de-energized condition it exhausts said exhaust manifold, whereas in its energized condition it closes off such exhaust.
 8. A pneumatic brake system as set forth in claim 1 wherein said exhaust valve means is integral with said equalizing reservoir charging means.
 9. A pneumatic brake system as set forth in claim 8 wherein said exhaust valve means comprises a duplex valve operable in one position to connect the source of compressed air to the equalizing reservoir for the charging thereof, and in the other position to disconnect the source of compressed air and connect the exhaust manifold to the equalizing reservoir for the exhaustion thereof.
 10. A pneumatic brake system as set forth in claim 9 wherein said exhaust valve is electrically energized, and further wherein the energization thereof causes a charging of the equalizing reservoir, whereas the de-energization thereof causes exhaustion of the equalizing reservoir.
 11. A pneumatic brake system as set forth in claim 10 and including a bypass in parallel with the exhaust valve said bypass having a check valve therein and providing fluid communication from the equalizing reservoir to the source of compressed air, thereby providing a means of exhausting the equalizing reservoir by proper manipulation of the charging means. 